Plastic trash bags are produced and sold on an extensive scale in a variety of shapes and sizes. The vast majority of these bags are made of polyethylene film. The bags in general include sidewalls that are often joined by one or more seams, a closed lower bottom end, and an open upper end. The trash bag can serve as a liner for a trashcan. Conventionally, an upper edge of the bag, which defines the open end, is rolled over an upper lip of the trashcan to position the bag in an open position and to secure the bag to the trashcan. It can be difficult to maintain the bag in the open position and in a secured relationship with respect to the top of the trashcan when the bag is loaded with trash.
The use of elastic means for securing the open end of a liner bag to the top edge of a trashcan is generally known. It is desirable for such an elastic top bag to provide adequate “grip” to the can to prevent the bag from falling into the can when loaded with trash. As a competing consideration, however, because the cost of the elastic component typically far outweighs the cost of the liner bag material, it is also desirable to limit the amount of elastic used to only that which is necessary to provide adequate grip. Furthermore, since most trash bags are packaged in rolls or in a highly folded condition, it is desirable that the incorporation of elastic means on a liner bag does not hinder conventional packaging techniques.
An attachment method used in the incontinence industry involves the intermittent bonding or “stitch attachment” of heat-activated elastic film material onto a substrate such that between every two bond regions there is a discernable unattached length of the heat activated elastic film material. The bonds are created by heat sealing or adhesive. This type of basic pattern can be reproduced to make spaced intervals or “stitches” of attached and unattached sections. Once the garment has been processed and activated (i.e., subjected to heat), the unattached portions of the elastic material shrink to provide a shirred and elastic garment. This attachment method can also be applied to making elastic top trash bags, such as shown in U.S. Pat. No. 5,120,138 to Midgley and International PCT Patent Application No. WO 00/39005 to Marchal.
Garment and diaper manufacturers typically apply pre-cut strips of the heat-activated elastic film material onto an article in a direction transverse to the direction of the article substrate in a production situation. This intermittent stitch attachment method has been applied to making elastic top trash bags. Such an attachment technique, however, can be impractical in the case of plastic bags produced by a conventional high-speed continuous bag machine because it involves the intermittent bonding of individual strip lengths of the elastic to discrete sections of a continuously moving web, making consistent alignment of the individual elastic strips with respect to the leading and trailing edges of successive bag sections of the moving web difficult to achieve. This problem is especially evident as the speed of the web varies during ramp up and ramp down operations of the bag production machinery.
Accordingly, there is a need in the art for an improved method of continuous production of elasticized liner bags which is cost effective, enables high speed operation, and is easily adaptable to existing bag machinery.